In recent years, in the field of a semiconductor manufacturing apparatus, downsizing of the apparatus, lowering of manufacturing cost, improvement in product quality, and the like, have been strongly demanded. In order to respond to those requirements, the development of an integrated processing apparatus that continuously carries out oxide film processing and polysilicon film processing, with respect to a wafer, has been proposed as a semiconductor manufacturing apparatus for the next generation.
However, in such an integrated processing apparatus, gaseous species to be supplied include thirty types of gases, which are varied in character, that is, in addition to gaseous species for etching in oxide film processing, corrosive gaseous species, such as HBr and C, as well are to be included in the gaseous species supplied. Therefore, prevention of backflow and back-diffusion in so-called switching between gaseous species, and improvement in the rate of gas utilization due to gas displacement at high speed, have grown to become more important matters.
Additionally, the applicant for the present patent has thus far developed many technologies relating to prevention of backflow and back-diffusion in switching of gaseous species to be supplied, such as those technologies disclosed below.
For example, Japanese Patent No. 3442604 shows an example thereof. As shown in FIG. 18, in the case where a plurality of gaseous species G1 to Gn to be supplied are switched by operating switching valves V1 to Vn, with (1) the supply line Ln of gaseous species at a minimum flow rate, which is disposed at a position most distant from a gas-out portion Go, (2) orifices S1 to Sn are provided to make the ratios between the passage areas of the respective lines L1 to Ln and the gas flow rates of the respective lines constant, or (3) a valve having an orifice OL built-in as shown in FIG. 19 is used as the switching valve Vn of the minimum flow rate line Ln. In order to increase a flow velocity of the gaseous species at the minimum flow rate, an attempt is made to prevent backflow and back-diffusion of another gas caused at the time of changing gaseous species by switching the switching valves V1 to Vn. For example, at the time of changing a gaseous species from the gas G3 to the gas G1 by simultaneously operating the switching valve V3 from open to close and the switching valve V1 from close to open, the gas G1 is prevented from flowing back to the upstream side of the switching valve V3.
Furthermore, Japanese Patent No. 3,387,777 is the invention in which all the switching valves V1 to Vn of FIG. 18 are orifice built-in type valves having a configuration as in FIG. 19, in which ratios of gas flow rates between the flow passage cross-sectional areas of the respective lines L1 to Ln of the respective gaseous species G1 to Gn and the gas flow rates of the respective lines L1 to Ln are made constant by changing the calibers of the orifices built in the respective switching valves V1 to Vn, to prevent backflow and back-diffusion caused by switching operations of the switching valves V1 to Vn. In FIG. 18, MFC denotes a thermal type flow rate control device, F denotes a filter, and RG denotes a pressure regulator.
In addition, it has been well-known that when an orifice is interposed in a flow passage, orifice built-in type valves are used, or a gasket type orifice is used as an orifice in a gas flow rate control device. However, a configuration in which orifices, or orifice built-in type valves, are used with the goal to prevent a high flow rate gas from flowing back and back-diffusing to the inside of a low flow rate gas line, in operation of the switching valves in a mixed gas supply device in which a plurality of gas supply lines are connected in parallel, and a mixed gas from the respective gas supply lines is supplied to a gas using place through a manifold, is limited to Japanese Patent No. 3442604 and Japanese Patent No. 3,387,777.